1. Field of the Invention
The present invention relates to an engineered process for manufacturing a CO2 capturing sorbent of calcium aluminum carbonate Ca—Al—CO3, and particularly to a process of manufacturing a carbon capturing agent which is obtained in batches of at least kilograms scale by controlling systematic experimental parameters. As fabricating material Ca—Al—CO3 is used to capture carbon dioxide at medium-high temperature (400˜800° C.) conditions.
2. Description of Related Art
It is a promising goal for international society to reach carbon dioxide reduction by carbon dioxide (CO2) capturing technology. The carbon capturing technology can be widely used in elevated temperature procedures relating to CO2 emissions in the industry, such as burning of coal and oil or gas adsorption enhanced reforming (AER), etc. From international experiences, it shows that the currently developing carbon capturing technologies are post-combustion process, which applies amine-based solvent such as ethanol amine at about 100 to 150° C. condition. The carbon capturing technology based on alkaline solvents have shortcomings of low carbon capturing amount, high energy consumption, corrosion to facility and unfriendliness to environment. In addition, a narrow capturing temperature range is also an important concern. As a great effort of the world adopting various technologies to slow down the CO2-related greenhouse effect, the extensive development of CO2 capture technology at different industries should prospectively become a trend, given an example of solid sorbent announced as the emerging technology in the upcoming 10 years by U.S. Department of Energy.
The solid sorbents have significant merits of a wide range of work temperatures from room temperature to 800° C., convenient for use and handling, and friendliness to environment. The CO2 capture capacity mainly depends on the temperature and the used material, affecting on its performance (Energy Environ. Sci., 2011, 4, 3805-3819). There are three categories: (1) at low temperature (<200° C.) such as carbon materials, zeolite, amine modified metal organic frames (MOFs), and alkali metal carbonate etc, with carbon capturing amount of 3.5-9.4 mmol/g;. (2) at medium temperature (200-400° C.), such as Mg—Al layered compounds (LDHs), K modified LDHs etc, with the carbon capturing amount of about 1.4 mmol/g; and (3) at medium-high temperature (>400° C.), such as CaO-containing alkaline ceramics, with the carbon capturing amount of 6.5-11.6 mmol/g.
Different CO2 sorbents exhibit wide application ranges. Basically, physical adsorption is occurred at low-temperature, and therefore has poor gas selectivity. To increase carbon capturing capacity, structural materials with high surface area such as of MCM-41, SBA-15 and MOF can be used as support. Thus, by incorporating alkaline groups and carriers, both of CO2 selectivity and capacity are improved. Lee (R.O.C. application No. 098107986) discloses the use of an amine-modified silicon substrate (MSPs) at 20-150° C. with maximum adsorption capacity of 102 mg/g (2.32 mmol/g). In addition, MgO-based sorbent are mainly used at medium temperature, a better CO2 sorption performance is usually achieved via modification. Hazard (J. Hazard Mater., 2012, 203, 341-347) discloses a mesoporous substrate modified by MgO, which reach the maximum adsorption amount of 131 mg/g (2.98 mmol/g) at 150-400° C.
The requirements of better carbon capturing agent at high temperatures must have a high carbon capturing amount, rapid rate, good stability and mechanical strength etc. To capture CO2 under medium-high temperature has advantages of wide CO2 concentrations, high capture amount and reasonable energy consumption and therefore is regarded as a very promising technology. Such a series of materials containing calcium oxide (CaO) have been most extensively studied with CO2 capture process including carbonation and regeneration steps.
However, the major technological bottleneck for elevated temperature CO2 capture is the improvement of high temperature stability of sorbent. As we known, CaO-based sorbents tend to deteriorate at high temperature and in high CO2 concentration. How to maintain the stability in high CO2 concentration and temperature is the key issue. Therefore, it is presently explored on post-combustion capture activity for majority of the researches and patents. For example: U.S. Patent Application No. 20120025134A1 discloses the synthesis of CaO/MgO series materials with conversion rate of higher than 90% for 600 min (15% CO2) at 800-900° C. R.O.C. Patent Application No. 099 116 724 discloses the use of CaO and other metal oxides in the carbon dioxide capturing system to obtain 99-100% CO2 removal rate (13-16% CO2) at 650° C. The above technology has improved CO2 capturing weight evenly at elevated temperature but of less than 16% CO2. Furthermore, most of them cannot afford sorbent production with kilo-scale, lacking the cost competition.
The present invention intends to use the co-precipitation method to manufacture the carbon capturing agent in yield of at least kilograms per batch. This sorbent is hydrophilic material with a lamella structure formed by Ca+2, Al+3, OH− and CO32−. After calcinations for removal layered ions, a mixed oxide with high CaO content is obtained. This sorbent exhibit a promising niche as applied to medium-high temperature of 400-800° C. under a wide concentration range of 5-100% CO2.
In order to solve the aforementioned problems, the inventors has studied and proceeded in-depth discussion, and actively seek approaches for many years engaged in the research and experiences of related industries and manufacturing. After long-term research and efforts in development, the inventors has finally the successfully accomplished this invention “an engineered process of manufacturing a calcium aluminum carbonate Ca—Al—CO3 as carbon capturing agent used at medium-high temperature” so as to improve the problem encountered in the prior art.